Thermodynamic modeling and mechanical properties of hybrid alkaline cement composites

Abstract

Hybrid alkaline cement composites (HACC) were developed to overcome the low compressive strength of hybrid alkaline cement. Synthesized with geopolymer and cement paste, HACC contains a larger amount of calcium and alkali-activator than general hybrid alkaline cement does. Although HACC can achieve higher compressive strength than geopolymer and cement paste, the phase assemblage and microstructure of the HACC remains elusive. The characteristics of HACC with various cement paste contents are examined by employing thermodynamic calculations and experimental techniques such as X-ray diffraction, thermogravimetric analysis, mercury intrusion porosimetry, and compressive strength tests. The obtained results provide new insight into the strength-developing mechanism of HACC by deriving microstructural information and phase assemblages. In particular, it is revealed that the ratio of N-A-S-H gels to C-(A)-S-H gels can affect the homogeneity of the HACC structure. As the HACC structure becomes more homogeneous, the porosity decreases resulting in higher compressive strength.